Earlier flowering and harvesting are important to increase the price of Japanese pepper (Zanthoxylum piperitum (L.) DC. f. inerme Makino). The present study was conducted to evaluate the effects of the temperature on the flowering time of Japanese pepper for earlier flowering and fruit harvesting. Potted seedlings were transferred to greenhouses with minimum temperatures of 5, 10 and 15°C after breaking of dormancy. The plants grown in the 15°C treatment reached the full bloom stage three weeks earlier than the plants grown in the 5°C treatment. The number of flowers per inflorescence did not differ between the treatments. Lock of sprouting was observed in the 15°C treatment, suggesting that the sprouting rate tended to be lower than that in the 10 and 5°C treatments. The cluster-bearing shoot rate (rate of shoots that sprouted and bore flowers in all the sprouts of fruiting mother shoots) for fruiting mother shoots with a length ranging from 10 to 30 cm in the 15°C treatment was significantly lower than that in the 5°C and 10°C treatments. Rapid increase of temperature to 15°C after breaking of dormancy led to earlier flowering, but reduced the number of flowers in Japanese pepper trees. Maintenance of a minimum temperature of 15°C after breaking of dormancy could promote early flowering and fruiting. However, the rate of cluster-bearing shoots was higher by the transfer to 10°C than to 15°C. These results suggested that the transfer of Japanese pepper trees to the greenhouse at 10°C may promote earlier flowering and increase the cluster-bearing shoot rate a long with reducing the cost of fuel.
The genus Dioscorea is considered to be one of the most difficult groups for cyto-taxonomic studies because of the large number and small size of the chromosomes. The objective of the present study was to develop an efficient method of chromosome observation by identifying the optimum time for collecting root samples containing large numbers of metaphase cells. In the present investigation, two breeders’ lines developed at IITA, TDa 98/01183 (D. alata) and TDr 95/18544 (D. rotundata) which were identified as tetraploids (2n = 4x = 40) were used. To take samples for observation, root tips were collected from vine cuttings and seed tuber sets. In the root cells obtained from the seed tuber sets of both cultivars, TDa 98/01183 and TDr 95/18544, two peaks in the frequency of metaphase cells appeared in the diurnal cycle of cell division. The first peak was observed at seven hours after sunrise (1:00pm) and the second at 19 hours after sunrise (1:00am). In the roots of the seedlings obtained from vine cuttings, the first peak of frequency of metaphase cells appeared at four hours after sunrise (10:00am) in both cultivars and the second peak at 16 hours (10:00pm) in TDa 98/01183, but at 13 hours in TDr 95/18544 (7:00pm). Based on the results obtained, a cycle of cell division is considered to exhibit a periodicity of about 12 hours. The present investigation enabled to identify the optimum times for collecting root tip samples from rooted vine cuttings and seed tuber sets. The findings may facilitate cytogenetic studies in yams.
Vietnam is one of the countries in the world that will be most negatively affected by the sea-level rise (SLR). The large agricultural population in the coastal areas of the country is already constrained by saltwater intrusion now, and will be more so by SLR in the future. In the coastal district of Nga Son, Thanh Hoa Province of Vietnam, the farmers had maintained their livelihood under the salinity constraint on salt-tolerant sedge (Cyperus spp.) plants sold for handicraft and mat-making. In recent years, however, their livelihood has been eroded by declines in productivity and quality of the sedge due to increased salinity intrusion and shortage of fresh water supply. The income from sedge was reduced to a greater extent in a group of communes that are closer to the Gulf of Tonkin than the other group of communes with less negative impacts. The farmers’ responses to these changes showed similarity and differences between the two groups of communes. The seasonal peak of rainfall has become later and the sedge harvest had to be delayed. The farmers’ capability to adapt to the hydrological and climatic changes thus depends on their local hydrological conditions mediated by their financial situation. These constraints could be ameliorated by financial and engineering supports at various institutional levels. Agronomic efforts could also ameliorate the problems via provision of better suited crops on an improved characterization of the local environmental conditions.
In Amorphophallus bulbifer and Amorphophallus muelleri, five seedlings develop sequentially in a year when seeds are sown, and two seedlings develop when bulbils are used as planting materials. This growth mode of release of multiple seedlings contrasts with the traditional growth mode of commonly grown konjak species, i.e. production of one corm by a single seedling. In the present study, the propagation rate and the bulking rate were compared between the relay seedling release mode and one seedling release mode. The propagation coefficients were 1, 10 and 330 when seed corms, bulbils and seeds were used as planting materials, respectively. The bulking rates were 6,000 and 100 when seeds and bulbils were planted, whereas 4-6 when seedlings were raised directly from a corm. Cultivation under greenhouse conditions enhanced the germination and prevented the onset of dormancy. As a result, the cultivation period was prolonged from 6 to 9-10 months. The prolongation of the growth period and the multiple seedling release mode may enable to produce a big corm within a year; two years earlier under greenhouse conditions than under fieldconditions. It is likely that the yield potential of cultivated species of konjak which is presently low could be enhanced if seedlings derived from seeds were grown in a greenhouse.
The Casparian strip refers to a modified cell wall with the deposition of suberin or lignin. The Casparian strip in the endodermis is considered to act as a barrier to dissolving ions, especially to the toxic ones, in the apoplast between the cortex and stele of plant root. The objective of the present study was to determine whether Casparian strips were present in all the plant parts of sago palm that is considered to be salt-resistant. Different positions and parts of the roots, petioles, rachis and leaflets of sago seedlings at the 10th leaf stage were observed. In the adventitious root, Casparian strips were found in the endodermal cell wall at 10 mm from the root tip and above it, and a suberin lamella was observed at 40 mm from the root tip and above it. The Casparian strip was also found in the endodermal cell walls near the root tip of lateral roots. A U-shaped thickening was detected in the cell wall of the endodermis in the mid- and basal parts of lateral roots. However, Casparian strips were not observed in the exodermis and aboveground parts such as the petiole, rachis and leaflet. The development of Casparian strips in the endodermis can be considered to be one of the important mechanical factors relating to the functional role of the avoidance mechanism for preventing the excess influx of Na+ into the stele and its translocation from root to shoot in sago palm.
Bacterial wilt (BW) caused by the soil-borne bacterium Ralstonia solanacearum E. F. Smith (species complex) is one of the most serious diseases of peppers in tropical and subtropical regions and in warm temperate regions such as Japan. The pepper cultivar, Kyoto-Manganji No. 1 (MDH) (Capsicum annuum L.), is a double haploid and was bred from a landrace in Kyoto Prefecture, Japan. Although it has been reported that MDH is resistant to BW, virulent BW strains such as KP9547 have recently affected the production of MDH. Therefore, we evaluated the resistance of MDH to BW based on three separate inoculation experiments using challenges with 42 virulent BW strains from various regions of Japan. Thirty-five strains were virulent to California Wonder (CW), a sensitive cultivar and 26 strains were virulent to MDH, a resistant cultivar. Seven strains from potato and tobacco plants were not virulent on pepper. The average disease indices of the three experiments were significantly lower for MDH than for CW. Therefore, MDH is considered to display a partial resistance. This is the first report of BW resistance test in a partially resistant pepper cultivar using various strains of Ralstonia solanacearum, which cover all the categories of races (1, 3 and 4), biovars (N2, 3 and 4) and phylotypes (I and IV) reported in Japan. Therefore, MDH may be useful as a standard for partial resistance to BW to evaluate the resistance of Capsicum germplasm and virulence of R. solanacearum strains.